What Caused the Dinosaur Extinction? • Hacker News Board

Re: What Caused the Dinosaur Extinction?

#31

Post by goatlover » Sun, Aug 12, 2018, 4:42 AM UTC

pfdietz wrote: post #21

ian0 wrote: post #16

Earlier quoted context omitted.

This struck me as precisely the type of thing that they were giving out about in the article. So I asked a geologist was there more to it. They said: The Cretaceous-Paleocene event is dated to 66m years ago [1]. The crater has been dated to 65m years ago [2]. The deccan traps was from 63-69m years ago with the bulk of activity 66m years ago [3]. Obviously both the volcano and the meteor were life-changing events. Of…

There is no evidence the dinosaurs were on their way out. The evidence is entirely consistent with abrupt extinction with no precursor decline. The global mass extinction killed things that can be much more precisely dated than dinosaurs. Forams, for example, go extinct right at the impact boundary, cut off like a knife.

The article states that some scientists disagree and have evidence to back their claim that life was on it's way out.

Re: What Caused the Dinosaur Extinction?

#32

Post by mr_toad » Sun, Aug 12, 2018, 4:59 AM UTC

This articles tone comes across as incredibly snide, sarcastic, and condescending. This is how it describes the impact theory:

‘Mystery solved’. ‘Scientists cheered’. ‘a heartwarming story about the integrity of the scientific method.’

It reads more like a snarky movie review than science journalism.

Re: What Caused the Dinosaur Extinction?

#33

Post by furins » Sun, Aug 12, 2018, 6:57 AM UTC

pfdietz wrote: post #21

ian0 wrote: post #16

Earlier quoted context omitted.

This struck me as precisely the type of thing that they were giving out about in the article. So I asked a geologist was there more to it. They said: The Cretaceous-Paleocene event is dated to 66m years ago [1]. The crater has been dated to 65m years ago [2]. The deccan traps was from 63-69m years ago with the bulk of activity 66m years ago [3]. Obviously both the volcano and the meteor were life-changing events. Of…

There is no evidence the dinosaurs were on their way out. The evidence is entirely consistent with abrupt extinction with no precursor decline. The global mass extinction killed things that can be much more precisely dated than dinosaurs. Forams, for example, go extinct right at the impact boundary, cut off like a knife.

Geologist here: I've studied in 1997-2003, than I've had a PhD in stratigraphy in 2007. I researched on a similar subject trying to identify what caused "dinosaurs" appearence (spoiler: another extinction event). At that time the two hypotheses, at least in Europe, were still presented as equally valid.

How these two phenomena can be equally the cause of the mass extinction at the end of Cretaceous?

Two reasons, at least. The first is the uncertainty about how rapid was the decline of Life. Any geologic date has an error, so it is extremely hard to assess the velocity of geological events. Around the K/T boundary most rock samples cannot be dated with a precision greater than a million year, that means that 2 separate events have the same probability to be coeval or separated by hundreds of thousands years with 95% confidence. In these case the uncertainty cannot allow us to distinguish an abrupt event from a slow one. More precisely, some rocks can actually be dated with an error of ~10000 years, like the iridium anomaly, or like the Deccan's lava but forams does not live inside lava. So you have to correlate events, to find proxy signals like changes in water geochemistry and so on. This increases uncertainties when dealing with fossils, and may be an easy way to denigrate palaeontological studies, but there are still evidences of a progressive decline.

The second reason is that the decline in marine ecosystems was sharp after the iridium anomaly, but we cannot explain why that precise impact killed big reptiles on sea and land whereas hundreds of other asteroids that hit the Earth during mesozoic had not. It was surely not the asteroid impact alone. There are evidences that all the mass extinction events are not instantaneous, but they are all related to a sequence of (misfortunated) events in rapid sequence. The emplacement of igneous provinces has proven to be a common menace for life on Earth. Asteroids too.

What we actually "read" in the rocks is that Deccan's traps paved the way, the Yucatan impact provided a massive stroke, and the closeness of these two events finished the survivors. In my opinion the "war" between scientists was more an US phenomenon related to their need to get access to NSF funds. The cool one got all.

Re: What Caused the Dinosaur Extinction?

#34

Post by Pica_soO » Sun, Aug 12, 2018, 7:57 AM UTC

ncmncm wrote: post #28

tl;dr: Stuff happened 65+ mya. Theories developed over past ~50 years. Human extinction due in 50 y to 0.5 my. Implication: there is no need to rush a conclusion. New evidence will continue to surface. We might be extinct before certainty arrives.

Where does that certainty arrive, that we will go out with a grandiose bang?

Why not instead, shrink and shrivel to a rat thing, adapted to live on planet sized garbage dump, optimized for continuous fighting with its peers and survival in a toxic environment. No need to think about tomorrow- god unwills it.

Occasionally, a head-albino is born, a demonic creature whos head is big enough to murder its mother and ask uncomfortable questions. Usually these are worshiped, then sacrificed and eaten to prevent the cycle from restarting a new.

History of a species, is not about show business. There rarely is somebody before or after who will read it.

Re: What Caused the Dinosaur Extinction?

#35

Post by pvaldes » Sun, Aug 12, 2018, 10:03 AM UTC

lkrubner wrote: post #10

Start with a 3 species model. Imagine a shallow, closed sea, in which there is a shark, a plesiosaur, and a bird. We need to explain why the shark and the bird survive, but the plesiosaur goes extinct. An asteroid hits somewhere, causing environmental change. For the rest of this comment, I'm going to refer to temperature as a short-hand way of referring to any environmental change. The shallow, closed sea is undergo…

There is an easier explanation. Because there are refuges for the shark and the bird.

The shark can go to the deep sea, more stable and breath there. The bird can fly away and high over the poisoned cloud. The mammals can go under the soil. The plesiosaur could swim away but needs return to the surface to breath. Their suitable habitat has vanished.

Re: What Caused the Dinosaur Extinction?

#36

Post by chr1 » Sun, Aug 12, 2018, 11:04 AM UTC

mr_toad wrote: post #32

This articles tone comes across as incredibly snide, sarcastic, and condescending. This is how it describes the impact theory: ‘Mystery solved’. ‘Scientists cheered’. ‘a heartwarming story about the integrity of the scientific method.’ It reads more like a snarky movie review than science journalism.

'snide, sarcastic, and condescending' was not just the authors view, but the way involved scientists view theories of each other. So it's unfair to blame the article for that, which is an article about a scientist and not science in general.

Re: What Caused the Dinosaur Extinction?

#37

Post by pfdietz » Sun, Aug 12, 2018, 11:24 AM UTC

samth wrote: post #24

pfdietz wrote: post #21

Earlier quoted context omitted.

There is no evidence the dinosaurs were on their way out. The evidence is entirely consistent with abrupt extinction with no precursor decline. The global mass extinction killed things that can be much more precisely dated than dinosaurs. Forams, for example, go extinct right at the impact boundary, cut off like a knife.

The article is, roughly, about a geologist who studies exactly forams and disagrees.

Yes, and others who study forams have looked at the same evidence and come to different conclusions. Someone's inferences are not following the same logic as others, and the most parsimonious explanation is that it's this person -- who I understand has become somewhat notorious -- not the rest of the scientific community.

Re: What Caused the Dinosaur Extinction?

#38

Post by Drdrdrq » Sun, Aug 12, 2018, 3:14 PM UTC

pfdietz wrote: post #37

samth wrote: post #24

Earlier quoted context omitted.

The article is, roughly, about a geologist who studies exactly forams and disagrees.

Yes, and others who study forams have looked at the same evidence and come to different conclusions. Someone's inferences are not following the same logic as others, and the most parsimonious explanation is that it's this person -- who I understand has become somewhat notorious -- not the rest of the scientific community.

And you know better because...?

The main point of the article is that the issue is far from settled, and that evidence for both sides is lacking. Until the consensus is reached through scientific means (instead of bullying) the matter is not closed.

Re: What Caused the Dinosaur Extinction?

#39

Post by stephengillie » Sun, Aug 12, 2018, 3:25 PM UTC

pfdietz wrote: post #37

samth wrote: post #24

Earlier quoted context omitted.

The article is, roughly, about a geologist who studies exactly forams and disagrees.

Yes, and others who study forams have looked at the same evidence and come to different conclusions. Someone's inferences are not following the same logic as others, and the most parsimonious explanation is that it's this person -- who I understand has become somewhat notorious -- not the rest of the scientific community.

Could you link to some of this purported notoriety?

Re: What Caused the Dinosaur Extinction?

#40

Post by stephengillie » Sun, Aug 12, 2018, 3:28 PM UTC

vertline2 wrote: post #14

pfdietz wrote: post #4

The evidence for a massive impact precisely at the K/T boundary is ironclad. Any alternate theory in which the impact was not causal has to explain how this incredible coincidence (the largest impact in the past 100 million years occurring in a layer deposited in just thousands of years, right at the boundary) occurred.

Is it possible for a meteor to cause a chain of volcanoes to blow? like all the pressure under the crust gets rattled around?

Maybe volcanic debris somehow interacted with a passing object (like Messenger-1) and changed its trajectory to pass through Earth?

It's very human to want to connect these events into a cohesive narrative, but there is still the possibility that they were independent events in our universe.